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llmshim

One interface, every LLM provider. The proxy server starts automatically — no setup needed.

Install

pip install llmshim

Configure

import llmshim

# Set API keys (writes to ~/.llmshim/config.toml — only needed once)
llmshim.configure(
    anthropic="sk-ant-...",
    openai="sk-...",
    gemini="AIza...",
    xai="xai-...",
    openrouter="sk-or-...",
)

Or from the CLI: llmshim configure

Self-hosted servers (vLLM / SGLang)

vLLM and SGLang are configured via environment variables (not config.toml) — the auto-spawned proxy inherits them from your Python process. Set them before your first call:

import os

os.environ["VLLM_BASE_URL"] = "http://localhost:8000/v1"
os.environ["VLLM_API_KEY"] = "..."       # optional
os.environ["SGLANG_BASE_URL"] = "http://localhost:30000/v1"
os.environ["SGLANG_API_KEY"] = "..."     # optional

Then address them via the model string — vllm/<served-model> or sglang/<served-model> (see the model table below).

Chat

import llmshim

resp = llmshim.chat("claude-sonnet-5-5", "What is Rust?")
print(resp["message"]["content"])

With options (all map to the API's provider-agnostic config):

resp = llmshim.chat(
    "openai/gpt-6-sol",
    "Explain quicksort",
    max_tokens=500,
    temperature=0.7,
    top_p=0.9,
    top_k=40,
    stop=["\n\n"],
    reasoning_effort="high",
)

With message history:

resp = llmshim.chat("claude-sonnet-5-5", [
    {"role": "system", "content": "You are a pirate."},
    {"role": "user", "content": "Hello!"},
], max_tokens=500)

Streaming

for event in llmshim.stream("claude-sonnet-5-5", "Write a poem"):
    if event["type"] == "content":
        print(event["text"], end="", flush=True)
    elif event["type"] == "reasoning":
        pass  # thinking tokens
    elif event["type"] == "usage":
        print(f"\n[↑{event['input_tokens']} ↓{event['output_tokens']}]")

Multi-Model Conversations

Switch models mid-conversation. History carries over.

messages = [{"role": "user", "content": "What is a closure?"}]

r1 = llmshim.chat("claude-sonnet-5-5", messages, max_tokens=500)
print(f"Claude: {r1['message']['content']}")

messages.append({"role": "assistant", "content": r1["message"]["content"]})
messages.append({"role": "user", "content": "Now explain differently."})

r2 = llmshim.chat("gpt-6-sol", messages, max_tokens=500)
print(f"GPT: {r2['message']['content']}")

Reasoning / Thinking

Two provider-agnostic knobs control reasoning; both are clamped to the nearest tier the target model supports:

  • reasoning_effort — "none", "low", "medium", "high", "xhigh", or "max"
  • reasoning_mode — "standard" (default) or "pro" (requests substantially more model work; native on OpenAI gpt-5.6/-pro, emulated as an effort bump elsewhere)
resp = llmshim.chat(
    "claude-sonnet-5-5",
    "Solve: x^2 - 5x + 6 = 0",
    max_tokens=4000,
    reasoning_effort="high",
    reasoning_mode="pro",
)
print(resp["reasoning"])        # thinking content
print(resp["message"]["content"])  # answer

For full native control, bypass the unified mapping with a namespaced provider_config (see below), e.g. provider_config={"x-anthropic": {"thinking": {"type": "adaptive"}, "output_config": {"effort": "high"}}}.

Provider-Specific Controls (provider_config)

provider_config merges into the request root and carries anything the unified config doesn't cover. Native provider controls MUST be namespaced per provider (x-anthropic, x-openai, x-gemini, x-openrouter, x-vllm, x-sglang); it also carries the top-level tools, response_format, and reasoning_summary keys.

resp = llmshim.chat(
    "anthropic/claude-sonnet-5-5",
    "Solve this step by step: 17 * 23",
    max_tokens=4000,
    provider_config={
        # native Anthropic adaptive-thinking control
        "x-anthropic": {"thinking": {"type": "adaptive"}, "output_config": {"effort": "high"}},
    },
)

OpenRouter routing preferences use the x-openrouter namespace:

resp = llmshim.chat(
    "openrouter/anthropic/claude-sonnet-5",
    "Hello",
    max_tokens=200,
    provider_config={"x-openrouter": {"provider": {"sort": "throughput"}}},
)

Tool Use / Function Calling

tools = [{
    "type": "function",
    "function": {
        "name": "get_weather",
        "description": "Get current weather",
        "parameters": {
            "type": "object",
            "properties": {"city": {"type": "string"}},
            "required": ["city"],
        },
    },
}]

resp = llmshim.chat("claude-sonnet-5-5", "Weather in Tokyo?", max_tokens=500, tools=tools)
for tc in resp["message"].get("tool_calls", []):
    print(f"{tc['function']['name']}({tc['function']['arguments']})")

Tools are accepted in OpenAI Chat Completions format and auto-translated to each provider's native format.

Fallback Chains

resp = llmshim.chat(
    "anthropic/claude-sonnet-5-5",
    "Hello",
    max_tokens=100,
    fallback=["openai/gpt-6-sol", "gemini/gemini-3.8-flash"],
)

Error Handling

Non-streaming errors (bad model, unknown provider, provider failures) raise LlmShimError, which carries the API's structured error fields:

try:
    llmshim.chat("unknown/model", "hi")
except llmshim.LlmShimError as e:
    print(e.status_code)  # 400
    print(e.code)         # "bad_request"
    print(e.message)      # human-readable message

Streaming errors that occur mid-stream instead arrive as an error event (event["type"] == "error"); an HTTP error before the stream starts still raises LlmShimError.

Types

Spec-faithful TypedDict definitions are available in llmshim.types (and the common ones are re-exported at the top level) for static type-checking:

from llmshim.types import ChatResponse, StreamEvent, Message, Config

resp: ChatResponse = llmshim.chat("claude-sonnet-5-5", "hi")

Available: ChatRequest, ChatResponse, Config, Message, ToolCall, Usage, ResponseMessage, ModelEntry, ModelsResponse, HealthResponse, ErrorResponse, and the StreamEvent union (ContentEvent, ReasoningEvent, ToolCallEvent, UsageEvent, DoneEvent, ErrorEvent).

Other

llmshim.models()   # list available models
llmshim.health()   # {"status": "ok", "providers": [...]}

How It Works

On first call, the package:

  1. Finds the llmshim binary (bundled, on PATH, or in repo)
  2. Lets the child bind a random localhost port and reads its private startup record
  3. Pins the child's one-time TLS certificate, authenticates every request, and keeps a parent-liveness pipe open
  4. Server stops automatically when Python exits

No Docker, no background services, no manual server management.

Development

The unit tests under tests/ are fully mocked — they run a local HTTP server returning canned JSON and SSE, so they need no API keys and make no real provider calls:

pip install httpx pytest
pytest tests/

test_e2e.py is a separate LIVE suite that spawns the real binary and makes billed provider calls; run it only when you deliberately want to hit real APIs.

Advertised Models

Provider Models
OpenAI gpt-6-astra, gpt-6-sol, gpt-6-luna
Anthropic claude-fable-5-1, claude-opus-5-5, claude-sonnet-5-5, claude-haiku-4-5-20251001
Gemini gemini-3.8-flash, gemini-3.5-flash-lite
xAI grok-4.6

Call llmshim.models() for the live list filtered to your configured providers.

OpenRouter & self-hosted (vLLM / SGLang)

These providers are addressed by the model string plus environment variables — any model the upstream serves is reachable, so they aren't in the table above.

Provider Address as Env vars Native controls
OpenRouter openrouter/<vendor>/<model> (e.g. openrouter/anthropic/claude-sonnet-5) OPENROUTER_API_KEY (or llmshim.configure(openrouter=...)) provider_config={"x-openrouter": {...}} (provider, models, transforms)
vLLM vllm/<served-model> VLLM_BASE_URL (+ optional VLLM_API_KEY) provider_config={"x-vllm": {...}}
SGLang sglang/<served-model> SGLANG_BASE_URL (+ optional SGLANG_API_KEY) provider_config={"x-sglang": {...}}

Metadata

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